test that we do not change the offset of ZST tuple fields when unsizing

src/test/ui/dynamically-sized-types/dst-tuple-zst-offsets.rs

@@ -0,0 +1,22 @@
+// run-pass
+
+#![feature(unsized_tuple_coercion)]
+
+// Check that we do not change the offsets of ZST fields when unsizing
+
+fn scalar_layout() {
+    let sized: &(u8, [(); 13]) = &(123, [(); 13]);
+    let unsize: &(u8, [()]) = sized;
+    assert_eq!(sized.1.as_ptr(), unsize.1.as_ptr());
+}
+
+fn scalarpair_layout() {
+    let sized: &(u8, u16, [(); 13]) = &(123, 456, [(); 13]);
+    let unsize: &(u8, u16, [()]) = sized;
+    assert_eq!(sized.2.as_ptr(), unsize.2.as_ptr());
+}
+
+pub fn main() {
+    scalar_layout();
+    scalarpair_layout();
+}